Tetralin isocyanates

ABSTRACT

The present invention relates to novel aromatic isocyanates obtained by partially hydrogenating naphthalene as well as the processes for preparing the same, and to their use as an isocyanate component in the production of polyurethanes.

FIELD OF THE INVENTION

The present invention relates to novel aromatic isocyanates obtained bypartially hydrogenating naphthalene as well as the processes forpreparing the same, and to their use as an isocyanate component in theproduction of polyurethanes.

BACKGROUND OF THE INVENTION

Among the organic polyisocyanates of commercial and economicsignificance as starting materials for polyurethanes, both rigid andflexible foams, in particular flexible foams, mixtures ofdiphenylmethane diisocyanate (MDI), polyphenylene polymethylenepolyisocyanates, prepolymers based on such materials, and toluenediisocyanate (TDI) are known to be suitable for preparing flexiblefoams. See, for example, U.S. Pat. Nos. 4,239,856, 4,256,849, 4,261,852and 4,365,025, 5,070,114, 4,478,960, 4,945,117, 5,369,138, 4,876,292,5,521,225.

Allophanate modified isocyanates are also known in the art. Variousisocyanates containing allophanate groups and processes for theirproduction are disclosed in, for example, U.S. Pat. Nos. 4,738,991,4,866,103, 5,319,053 and 5,319,054, and European Patents 0,031,650 and0,393,903.

An improved isocyanate was required to have improved physical propertiesover TDI, so it needed to be liquid (an advantage over MDI) and have avapor pressure higher than TDI (hence it's higher molecular weightstructure). Surprisingly, such a foam also exhibited improvement in foamproperties.

Foams of varying hardness, reasonable physical properties and good humidaged compression sets can be formulated with the present tetralinisocyanates. Physical properties such as elongation and tear wereimproved.

SUMMARY OF THE INVENTION

The present invention relates to isocyanates corresponding to theformula:

wherein

n is a number from 1 to 2.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to isocyanates corresponding to theformula:

wherein n is 1 or 2.

When n=1, the isocyanate can be 2- or 3-tetralin isocyanate. When n=2,the isocyanate can be 2,3-tetralin diisocyanate, 2,4-tetralindiisocyanate, 3,4-tetralin diisocyanate, 2,5-tetralin diisocyanate, ormixtures thereof.

The novel isocyanates of the present invention are produced by reactingtetralindiamine with phosgene. The starting diamines can be produced byprocesses already known (See “Nitrobenzene and Nitrotoluenes”,Kirk-Othmer Encyclopedia of Chemical Technology, 4^(th) ed, vol 17, 1996and “Diaminotoluenes”, ibid, vol 2, 1992.). For example,tetrahydronaphthalene (tetralin) can be converted to the diamine bycatalytic hydrogenation. In particular, the reaction of tetralin withnitric acid results in dinitrotetralin, which then is catalyticallyhydrogenated to give tetralindiamine.

Tetrahydronaphthalene is a commercially available product, which can bemade by partially hydrogenating naphthalene.

The above-diamine is converted to the isocyanate of the presentinvention by reacting it with phosgene. Phosgene may be employed ineither liquid or gaseous form, preferably liquid form. Thetetralindiamine is dissolved in a mixture of diglyme/1,2-dichlorobenzeneand added to the phosgene solution. The temperature of the reactionmedium ranges from about 90 to 190° C., preferably from 110 to 170° C.

The tetralin di or isocyanate can also be made from the amine usingphosgene free approaches such as urethane splitting.

The novel isocyanate of the present invention may be used in the samefields as aromatic polyisocyanates of prior art have been used. Forexample, it can be used in the fields such as polyurethane by reactingvarious compounds, including polymers, containing active hydrogen groupssuch as polyols, as well as intermediates, for producing other novelcompounds or polymers, and so on. The new isocyanates according to thepresent invention may be used instead of TDI and/or MDI in all processesfor the production of polyurethanes using these known polyisocyanates.

EXAMPLES

The invention is described in more detail with the aid of the followingexamples.

Example 1

Preparation of Tetralin Diamine

A 2,000 g quantity of nitric acid solution (39.2% by weight in sulfuricacid) was added to a 5 liter flask. 1,2,3,4-Tetrahydronaphthalene(tetralin) was slowly added, maintaining a temperature of 70° C. Thereaction mixture was stirred at 70° C. for three (3) hours, then washedwith water (2×1L) and 10% sodium bicarbonate (2×0.5L). Thedinitrotetralin was dried and reacted with hydrogen at 1,500 psig and160° C. for two (2) hours to give tetraline diamine.

Example 2

Preparation of Tetralin Diisocyanate

1,2-dichlorobenzene(1.5L) was cooled to 0° C. and phosgene added at arate of 3 moles/hour for 1.8 hours. Tetralin diamine (150 g) wasdissolved in a 50:50 mixture of diglyme/1,2-dichlorobenzene and added tothe phosgene solution. The reaction solution was slowly heated to 135°C. and held at that temperature for 1 hour. The resulting mixture waspurged with nitrogen and the solvent was vacuum distilled (134-136° C.at 2.7 mmHg) to give a light yellow liquid with a % NCO content of 34.5.

Example 3

Polyurethane Foams Using Tetralin Diisocyanate

The table below illustrates the results obtained when tetralindiisocyanate was used in a standard TDI foam formulation. TDI was alsofoamed to give a control sample. The polyol used is a glycerin/propyleneglycol based polyol with a hydroxyl number of 56. The catalyst is amixture comprised of Dabco T-9, Dabco T-12, and Polycat 70. L-620 is asilicone surfactant.

As can be seen, the tensiles were very similar. In addition, thetetralin diisocyanate showed a 24% improvement in both the elongationand tear strength.

TABLE 1 Tetralin ISO TDI Diisocyanate Index 100 100 Formulations: Polyol100 100 Water 4.00 4.40 L-620 0.8 0.8 Catalyst 0.5 1.0 Foam Properties:Density, pcf 1.30 1.31 Tensile, psi 17.7 17.3 Elongation, % 168 208Tears, lbs/in 1.72 2.13

Although the invention has been described in detail in the foregoing forthe purpose of illustration, it is to be understood that such detail issolely for that purpose and that variations can be made therein by thoseskilled in the art without departing from the spirit and scope of theinvention except as it may be limited by the claims.

What is claimed is:
 1. Isocyanates corresponding to the formula:

wherein n is 1 or
 2. 2. A process for preparing isocyanatescorresponding to the formula:

wherein n is 2 comprising the steps of: a) reacting1,2,3,4-tetrahydronaphthalene with nitric acid to producedinitrotetralin; b) catalytically hydrogenating dinitrotetralin toproduce tetralin diamine. c) phosgenating tetralindiamine to produce aresulting product; and d) distilling said resulting product.